Transmission and reception of a wideband signal with narrowband interference

ABSTRACT

It is disclosed a method including accommodating, in frequency domain, a first bandwidth of a first carrier signal with respect to a second bandwidth of a second carrier signal such that the first bandwidth adjoins to or overlaps the second bandwidth, the first bandwidth being greater than the second bandwidth. In a further aspect, prior to the transmission, the interference of the modulated second carrier signal is subtracted from each of the plurality of subcarrier signals of the first carrier signal.

FIELD OF THE INVENTION

The present invention relates to signal transmission and reception. Morespecifically, the present invention relates to methods, apparatuses, asystem and a related computer program product for signal transmissionand receptions. Examples of the present invention may be applicable e.g.to cellular systems such as 3GPP (3^(rd) generation partnership project)LTE (long term evolution).

BACKGROUND

Currently, extensions to the LTE Release 8 standard are discussed forfuture releases, like LTE Release 9 or IMT (international mobiletelephony) advanced/LTE-Advanced, e.g. in order to increase systemperformance.

At the same time, there may be different application scenarios for LTEsystems in different frequency bands. Specifically, the tightcooperation of LTE with GSM (global system for mobile communications)transmissions may be considered as such a cooperation allows forproviding full coverage GSM systems in combination with high performanceLTE radio air interfaces.

For example, as the minimum LTE bandwidth may be 1.4 MHz in a system, itwill be difficult to accommodate e.g. an additional GSM carrier of 200KHz bandwidth in this same frequency band of 1.6 MHz, as there will bestrong frequency guard bands required to avoid inter systeminterference.

However, if a GSM carrier and an LTE carrier are used in close-byfrequency bands or even in the same frequency band, there may be stronginterference due to mutual out-of-band emissions. As GSM has a muchsmaller bandwidth of only 200 KHz compared to e.g. 10 or 20 MHz for LTE,the main interference may stem from GSM to the LTE system under theassumption that both carriers have substantially the same overalltransmit power.

In consideration of the above, it is an object of examples of thepresent invention to overcome one or more of the above drawbacks. Inparticular, the present invention provides methods, apparatuses, asystem and a related computer program product for signal transmissionand reception.

According to an example of the present invention, in a first aspect,this object is for example achieved by a method comprising:

accommodating, in frequency domain, a first bandwidth of a first carriersignal with respect to a second bandwidth of a second carrier signalsuch that the first bandwidth adjoins to or overlaps the secondbandwidth, the first bandwidth being greater than the second bandwidth.

According to further refinements of the example of the present inventionas defined under the above first aspect,

the method further comprises transmitting the first and second signalsfrom a single means for transmitting;

the method further comprises transmitting the first and second signalsfrom a plurality of means for transmitting in a coordinated manner.

According to an example of the present invention, in a second aspect,this object is for example achieved by a method comprising:

transmitting a transmission signal comprising a plurality of subcarriersignals of a first carrier signal, each of which subcarrier signalsbeing subtracted by an effective interference of a modulated secondcarrier signal.

According to further refinements of the example of the present inventionas defined under the above second aspect,

the method further comprises, prior to the transmitting, subtracting theeffective interference of the modulated second carrier signal from eachof the plurality of subcarrier signals of the first carrier signal;

the method further comprises, prior to the transmitting, filtering themodulated second carrier signal for removing the subcarrier signalsoverlapping the modulated second carrier signal in bandwidth;

the method further comprises, after the subtracting and prior to thetransmitting transforming a result signal resulting from the subtractingfrom frequency domain into time domain, inserting time intervals intothe transformed result signal, and combining the result signal beingtransformed and inserted with time intervals with the filtered andmodulated second carrier signal to form the transmission signal;

the method further comprises, after the filtering and prior to thesubtracting, transforming the modulated first carrier signal from timedomain into frequency domain;

the method further comprises, after the transforming, calculating, byfiltering the transformed and modulated second carrier signal, aresulting distortion from the second carrier signal to the first carriersignal based on at least one of timing information and channelinformation.

According to an example of the present invention, in a third aspect,this object is for example achieved by a method comprising:

retrieving a first carrier signal from a received transmission signalcomprising a plurality of subcarrier signals of the first carriersignal, each of which subcarrier signals being interfered by aneffective interference of a modulated second carrier signal.

According to further refinements of the example of the present inventionas defined under the above third aspect,

the method further comprises, prior to the retrieving, receiving thetransmission signal;

the retrieving is performed by subtracting a generated replica of thesecond carrier signal from the received transmission signal;

the method further comprises, prior to the subtracting, generating thereplica of the second carrier signal by demodulating the decodedtransmission signal, decoding the received transmission signal, andfiltering the demodulated and decoded transmission signal for removingthe subcarrier signals overlapping the modulated second carrier signalin bandwidth;

the retrieving further comprises, after the subtracting, transforming asignal resulting from the subtracting from time domain into frequencydomain;

the method further comprises, after the receiving and prior to theretrieving, queuing the received transmission signal;

the retrieving is performed by decoding the received transmissionsignal, filtering the decoded transmission signal for removing thesubcarrier signals overlapping the modulated second carrier signal inbandwidth, detecting a midamble in at least one signal burst of thesecond carrier signal based on a reference midamble, extracting themidamble from the current signal burst, estimating current channelinformation from the extracted midamble, and processing symbols sent viathe first carrier signal based on the estimated current channelinformation during a subsequent burst of the second carrier signal afterthe at least one burst.

According to an example of the present invention, in a fourth aspect,this object is for example achieved by a method comprising:

distributing, in unoccupied control channel elements of a first carriersignal having a first bandwidth, at least a portion of a second carriersignal having a second bandwidth by using different control channelconfigurations in at least one neighboring cell, the first bandwidthbeing greater than the second bandwidth.

According to further refinements of the example of the present inventionas defined under the above first to fourth aspects,

the first carrier signal is a long term evolution carrier signal;

the second carrier signal is a global system for mobile communicationscarrier signal;

the transforming from time domain into frequency domain is one of aFourier transformation and a fast Fourier transformation;

the transforming from frequency domain into time domain is one of aninverse Fourier transformation and an inverse fast Fouriertransformation;

the timing information is an orthogonal frequency division multiplexingguard interval;

the channel information is channel state information;

the queuing is performed based on a first in first out queue.

According to an example of the present invention, in a fifth aspect,this object is for example achieved by an apparatus comprising:

means for accommodating, in frequency domain, a first bandwidth of afirst carrier signal with respect to a second bandwidth of a secondcarrier signal, the first bandwidth adjoining to or overlapping thesecond bandwidth, and the first bandwidth being greater than the secondbandwidth.

According to further refinements of the example of the present inventionas defined under the above fifth aspect,

the apparatus further comprises a single means for transmitting thefirst and second signals;

the apparatus further comprises a plurality of means for transmittingthe first and second signals in a coordinated manner;

the or each means for transmitting is constituted by a radio frequency,power amplifier and antenna chain.

According to an example of the present invention, in a sixth aspect,this object is for example achieved by an apparatus comprising:

means for transmitting a transmission signal comprising a plurality ofsubcarrier signals of a first carrier signal, each of which subcarriersignals being subtracted by an effective interference of a modulatedsecond carrier signal.

According to further refinements of the example of the present inventionas defined under the above sixth aspect,

the apparatus further comprises means for subtracting, prior to thetransmitting performed by the means for transmitting, the effectiveinterference of the modulated second carrier signal from each of theplurality of subcarrier signals of the first carrier signal;

the apparatus further comprises means for filtering, prior to thetransmitting performed by the means for transmitting, the modulatedsecond carrier signal for removing the subcarrier signals overlappingthe modulated second carrier signal in bandwidth;

the apparatus further comprises means for transforming, after thesubtracting performed by the means for subtracting and prior to thetransmitting performed by the means for transmitting, a result signalresulting from the subtracting from frequency domain into time domain,means for inserting, after the subtracting performed by the means forsubtracting and prior to the transmitting performed by the means fortransmitting, time intervals into the transformed result signal, andmeans for combining, after the subtracting performed by the means forsubtracting and prior to the transmitting performed by the means fortransmitting, the result signal being transformed and inserted with timeintervals with the filtered and modulated second carrier signal to formthe transmission signal;

the apparatus further comprises means for transforming, after thefiltering performed by the means for filtering and prior to thesubtracting performed by the means for subtracting, the modulated firstcarrier signal from time domain into frequency domain;

the apparatus further comprises means for calculating, after thetransforming performed by the means for transforming and by filteringthe transformed and modulated second carrier signal, a resultingdistortion from the second carrier signal to the first carrier signalbased on at least one of timing information and channel information.

According to an example of the present invention, in a seventh aspect,this object is for example achieved by an apparatus comprising:

means for retrieving a first carrier signal from a received transmissionsignal comprising a plurality of subcarrier signals of the first carriersignal, each of which subcarrier signals being interfered by aneffective interference of a modulated second carrier signal.

According to further refinements of the example of the present inventionas defined under the above seventh aspect,

the apparatus further comprises means for receiving the transmissionsignal prior to the retrieving performed by the means for retrieving;

the means for retrieving further comprises means for subtracting agenerated replica of the second carrier signal from the receivedtransmission signal;

the apparatus further comprises means for generating, prior to thesubtracting performed by the means for subtracting, the replica of thesecond carrier signal, the means for generating comprising means fordemodulating the decoded transmission signal, means for decoding thereceived transmission signal, and means for filtering the demodulatedand decoded transmission signal for removing the subcarrier signalsoverlapping the modulated second carrier signal in bandwidth;

the means for retrieving further comprises means for transforming, afterthe subtracting performed by the means for subtracting, a signal outputby the means for subtracting from time domain into frequency domain;

the apparatus further comprises means for queuing the receivedtransmission signal after the receiving performed by the means forreceiving and prior to the retrieving performed by the means forretrieving;

the means for retrieving comprises means for decoding the receivedtransmission signal, means for filtering the decoded transmission signalfor removing the subcarrier signals overlapping the modulated secondcarrier signal in bandwidth, means for detecting a midamble in at leastone signal burst of the second carrier signal based on a referencemidamble, means for extracting the midamble from the current signalburst, means for estimating current channel information from theextracted midamble, and means for processing symbols sent via the firstcarrier signal based on the estimated current channel information duringa subsequent burst of the second carrier signal after the at least oneburst.

According to an example of the present invention, in an eighth aspect,this object is for example achieved by an apparatus comprising:

means for distributing, in unoccupied control channel elements of afirst carrier signal having a first bandwidth, at least a portion of asecond carrier signal having a second bandwidth by using differentcontrol channel configurations in at least one neighboring cell, thefirst bandwidth being greater than the second bandwidth.

According to further refinements of the example of the present inventionas defined under the above fifth to eighth aspects,

the first carrier signal is a long term evolution carrier signal;

the second carrier signal is a global system for mobile communicationscarrier signal;

the transforming from time domain into frequency domain is one of aFourier transformation and a fast Fourier transformation;

the transforming from frequency domain into time domain is one of aninverse Fourier transformation and an inverse fast Fouriertransformation;

the timing information is an orthogonal frequency division multiplexingguard interval;

the channel information is channel state information;

the means for queuing is configured to queue based on a first in firstout queue;

at least one, or more of means for accommodating, means fortransmitting, means for subtracting, means for filtering, means forcalculating, means for combining, means for transforming, means forinserting, means for retrieving, means for receiving, means forgenerating, means for queuing, means for modulating, means fordemodulating, means for decoding, means for detecting, means forextracting, means for estimating, means for processing, means fordistributing and the apparatus is implemented as a chipset or module.

According to an example of the present invention, in a ninth aspect,this object is for example achieved by a system comprising:

a transmission apparatus according to the above sixth aspect;

an accommodating apparatus according to the above fifth aspect;

a receiving apparatus according to the above seventh aspect; and

a distributing apparatus according to the above eighth aspect.

According to an example of the present invention, in a tenth aspect,this object is for example achieved by a computer program productcomprising code means for performing method steps of a method accordingto any one of the above first to fourth aspects, when run on aprocessing means or module.

In this connection, it has to be pointed out that examples of thepresent invention enable one or more of the following:

Alleviating a need for separation of the LTE spectrum into two or moredifferent LTE carriers;

Alleviating a need for insertion of rather large (frequency) guard bandsto separate LTE and GSM systems from each other;

Enhancing overall spectral efficiency of the system concept;

Complying with a legacy GSM receiver, since the interference due to theLTE signal is mainly blocked due to according receiver filters, andsince the residual LTE out of band interference is very small;

Providing full GSM coverage;

Effectively combining LTE and GSM signals, such that specifically GSMmight be included into the LTE signal at an arbitrary place of thespectrum, e.g. at suitable positions for reducing the interference oncontrol channels.

Allowing support of UEs (user equipments) by pre-coding, which UEs arenot aware of the combined LTE-GSM transmission. This may be facilitatedby CSI (channel state information) that may be available;

Enabling interference cancellation in the UEs e.g. by implementing a GSMdecoder. Additionally, corresponding control signals and messages aredefined e.g. for broadcasting of the location of the GSM carrier.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of the present invention are described herein below withreference to the accompanying drawings, in which:

FIG. 1 shows methods according to an example of the present inventionfor signal transmission and reception;

FIG. 2 shows an alternative method according to an example of thepresent invention for signal transmission and reception;

FIG. 3 shows an apparatus according to an example of the presentinvention for accommodating e.g. a GSM carrier signal into an LTEcarrier signal using e.g. mutual interference between the GSM and LTEcarriers;

FIG. 4 shows an apparatus according to an example of the presentinvention for transmitting using e.g. pre-compensated combined GSM-LTEsignal generation;

FIG. 5 shows resulting interference e.g. from GMSK (Gaussian minimumshift keying) to an LTE OFDM signal according to the apparatus shown inFIG. 4;

FIG. 6 shows an apparatus according to an example of the presentinvention for receiving and retrieving using e.g. a time domain approachfor combined GSM and LTE transmission;

FIG. 7 shows an alternative apparatus according to an example of thepresent invention for receiving and retrieving using e.g. CSI basedcancellation of GSM interferer(s);

FIG. 8 shows a delay reduction according to the apparatus shown in FIG.7; and

FIG. 9 shows an alternative method and apparatus according to an exampleof the present invention using e.g. prohibited and available narrowbandembedding regions aligned with respect to UL (uplink) and DL (downlink).

DETAILED DESCRIPTION OF THE PRESENT INVENTION

Examples of the present invention are described herein below by way ofexample with reference to the accompanying drawings.

It is to be noted that for this description, the terms “long termevolution carrier signal; global system for mobile communicationscarrier signal; (fast) Fourier transformation; inverse (fast) Fouriertransformation; orthogonal frequency division multiplexing guardinterval; channel state information; and first in first out queue” areexamples for “first carrier signal; second carrier signal; transformingfrom time domain into frequency domain; transforming from frequencydomain into time domain; timing information; the channel information;and queuing”, respectively, without restricting the latter-named termsto the special technical or implementation details imposed to thefirst-named terms.

FIGS. 1 and 2 show methods for signal transmission and receptionaccording to an example of the present invention. Signaling betweenelements is indicated in horizontal direction, while time aspectsbetween signaling may be reflected in the vertical arrangement of thesignaling sequence as well as in the sequence numbers. It is to be notedthat the time aspects indicated in FIGS. 1 and 2 do not necessarilyrestrict any one of the method steps shown to the step sequenceoutlined. This applies in particular to method steps that arefunctionally disjunctive with each other. Within FIGS. 1 and 2, for easeof description, means or portions which may provide main functionalitiesare depicted with solid functional blocks or arrows and/or a normalfont, while means or portions which may provide optional functions aredepicted with dashed functional blocks or arrows and/or an italic font.

As shown in FIGS. 1 and 2, a communication system 200 may comprise atransmitter 201 according to an example of the present invention (suchas a BS (base station)), a receiver 202 (such as a UE) according to anexample of the present invention, a transmitter 201′ (see also FIG. 6)and a receiver 202′.

In an optional step S1-0, e.g. the transmitter 201 filtering a modulatedsecond carrier signal for removing subcarrier signals overlapping themodulated second carrier signal in bandwidth.

In an optional step S1-1, e.g. the transmitter 201 may performtransforming the modulated first carrier signal from time domain intofrequency domain (e.g. by a (F)FT).

In a further optional step S1-2, e.g. the transmitter 201 may performcalculating, e.g. by filtering the transformed and modulated secondcarrier signal, a resulting distortion from the second carrier signal tothe first carrier signal based on at least one of timing information(e.g. OFDM GI) and channel information (e.g. CSI).

In an optional step S1-3, e.g. the transmitter 201 may performsubtracting the effective interference of the modulated second carriersignal from each of the plurality of subcarrier signals of the firstcarrier signal.

Then, in optional steps S1-4 a to S1-4 c, e.g. the transmitter 201 mayperform transforming a result signal resulting from the subtracting fromfrequency domain into time domain (IFFT), inserting time intervals intothe transformed result signal; and combining the result signal beingtransformed and inserted with time intervals with the filtered andmodulated second carrier signal to form the transmission signal.

In step S1-5, e.g. the transmitter 201 may perform transmitting thetransmission signal comprising a plurality of the subcarrier signals ofthe first carrier signal (LTE), each of which subcarrier signals beingsubtracted by the effective interference of the modulated second carriersignal (GMSK).

Alternatively, in step S2-0, e.g. an accommodator (or means foraccommodating) 203 shown in FIG. 3 (described in more detail hereinbelow) may perform accommodating (S2-0), in frequency domain, a firstbandwidth of a first carrier signal (LTE carrier) with respect to asecond bandwidth of a second carrier signal (GSM carrier) such that thefirst bandwidth adjoins to or overlaps the second bandwidth, the firstbandwidth being greater than the second bandwidth.

E.g. in case the transmission signal from the transmitter 201′ has aform given by the accommodator, in an optional step S3-0, e.g. thereceiver 202 may perform receiving a transmission signal comprising aplurality of subcarrier signals of the first carrier signal, each ofwhich subcarrier signals being interfered by an effective interferenceof a modulated second carrier signal (GMSK).

Then, in an optional step S3-1, e.g. the receiver 202 may performqueuing the received transmission signal.

Thus, in step S3-2, e.g. the receiver 202 may perform retrieving thefirst carrier signal (e.g. LTE) from the received transmission signal.

Then, in an optional step S3-3, e.g. the receiver 202 may performgenerating a replica of the second carrier signal. The generatingperformed may comprise, in optional steps S3-4 a to S3-4 c, demodulating(S3-4 a) the received transmission signal; decoding the demodulatedtransmission signal, and filtering the demodulated and decodedtransmission signal for removing the subcarrier signals overlapping themodulated second carrier signal in bandwidth.

Then, in an optional step S3-5, e.g. the receiver 202 may performsubtracting the generated replica of the second carrier signal from thereceived transmission signal.

Finally, in an optional step S3-6, e.g. the receiver may performtransforming the signal resulting from the subtracting from time domaininto frequency domain.

Alternatively, as shown in FIG. 2, the receiver 202 may also perform theretrieving by performing, in optional steps S3-2 a to S3-2 f, decodingthe received transmission signal, filtering the decoded transmissionsignal for removing the subcarrier signals overlapping the modulatedsecond carrier signal in bandwidth, detecting a midamble in at least onesignal burst of the second carrier signal based on a reference midamble,extracting the midamble from the current signal burst, estimatingcurrent channel information from the extracted midamble; and processingsymbols sent via the first carrier signal based on the estimated currentchannel information during a subsequent burst of the second carriersignal after the at least one burst.

Finally, as shown in FIG. 9, another example of the present inventionmay also cover distributing, in unoccupied control channel elements ofthe first carrier signal having the first bandwidth, at least a portionof the second carrier signal having the second bandwidth by usingdifferent control channel configurations in at least one neighboringcell, the first bandwidth being greater than the second bandwidth.

As for further refinements of the methods according to an example of thepresent invention, the first carrier signal may be a long term evolutioncarrier signal, and the second carrier signal may be a global system formobile communications carrier signal. In addition, the transforming fromtime domain into frequency domain may be a (fast) Fouriertransformation, and the transforming from frequency domain into timedomain may be an inverse (fast) Fourier transformation. Still further,the timing information may an orthogonal frequency division multiplexingguard interval, and the channel information may channel stateinformation. Moreover, the queuing may be performed based on a first infirst out queue. Finally, the transmitting of the first and secondsignals may be from a single means for transmitting or from a pluralityof means for transmitting in a coordinated manner.

FIGS. 3 to 8 show apparatuses (e.g. transmitter 201, transmitter 201′,receiver 202 and accommodator 203) for signal transmission and receptionaccording to an example and an alternative example of the presentinvention. Within those Figs, for ease of description, means or portionswhich may provide main functionalities are depicted with solidfunctional blocks or arrows and a normal font, while means or portionswhich may provide optional functions are depicted with dashed functionalblocks or arrows and an italic font.

The transmitter 201 may comprise a transmitting antenna (or means fortransmitting) 2011, a modulator (or means for modulating) 2012, alow-pass filter (or means for filtering) 2013, a transformer (or meansfor transforming) 2014, an SC filter for calculating (or means forcalculating) 2015, an inverse transformer (or means for transforming)2016, an inserter (or means for inserting) 2017, a combiner (or meansfor combining) 2018 and a subtractor (or means for subtracting) 2019.

The receiver 202 may comprise a retriever (or means for retrieving)2021, a generator (or means for generating) 2022, a receiving antenna(or means for receiving) 2023, a demodulator (or means for demodulating)2024, a modulator (or means for modulating) 2025, a low-pass filter (ormeans for filtering) 2026, a FIFO (or means for queuing) 2027, asubtractor (or means for subtracting) 2028 and a transformer (or meansfor transforming) 2029.

Optionally, e.g. the means for filtering 2013 of the transmitter 201 mayperform filtering a modulated second carrier signal for removingsubcarrier signals overlapping the modulated second carrier signal inbandwidth.

Also optionally, e.g. the means for transforming 2014 of the transmitter201 may perform transforming the modulated first carrier signal fromtime domain into frequency domain (e.g. by a (F)FT).

Optionally, e.g. the means for calculating 2015 of the transmitter 201may perform calculating, e.g. by filtering the transformed and modulatedsecond carrier signal, a resulting distortion from the second carriersignal to the first carrier signal based on at least one of timinginformation (e.g. OFDM GI) and channel information (e.g. CSI).

Optionally, e.g. the means for subtracting 2019 of the transmitter 201may perform subtracting the effective interference of the modulatedsecond carrier signal from each of the plurality of subcarrier signalsof the first carrier signal.

Then, e.g. the means for transforming 2016 of the transmitter 201 mayperform transforming a result signal resulting from the subtracting fromfrequency domain into time domain (IFFT), e.g. the means for inserting2017 of the transmitter 201 may perform inserting time intervals intothe transformed result signal, and e.g. the means for combining 2018 ofthe transmitter 201 may perform combining the result signal beingtransformed and inserted with time intervals with the filtered andmodulated second carrier signal to form the transmission signal.

Then, e.g. the means for transmitting 2011 of the transmitter 201 mayperform transmitting the transmission signal comprising a plurality ofthe subcarrier signals of the first carrier signal (LTE), each of whichsubcarrier signals being subtracted by the effective interference of themodulated second carrier signal (GMSK).

Alternatively, as shown in FIGS. 3 and 6, e.g. an accommodator (or meansfor accommodating) 203 may perform accommodating, in frequency domain, afirst bandwidth of a first carrier signal (e.g. LTE carrier) withrespect to a second bandwidth of a second carrier signal (e.g. GSMcarrier) such that the first bandwidth adjoins to or overlaps the secondbandwidth, the first bandwidth being greater than the second bandwidth.As shown in FIG. 3, in a case i), the second carrier signal (e.g. LTEsignal carrier) may fully overlap the second carrier signal (e.g. GSMcarrier); in a case ii), the second signal may overlap the first signalpartially; and in a case iii), the second signal may adjoin to the firstsignal.

Optionally, e.g. in case the transmission signal from the transmitter201′ has a form given by the accommodator 203, e.g. the means forreceiving 2023 of the receiver 202 may perform receiving a transmissionsignal comprising a plurality of subcarrier signals of the first carriersignal, each of which subcarrier signals being interfered by aneffective interference of a modulated second carrier signal (GMSK).

Then optionally, e.g. the means for queuing 2027 of the receiver 202 mayperform queuing the received transmission signal.

Thus, e.g. the means for retrieving 2021 of the receiver 202 may performretrieving the first carrier signal (e.g. LTE) from the receivedinterfered transmission signal.

Optionally, e.g. the means for generating 2022 of the means forretrieving 2022 may perform generating a replica of the second carriersignal. The means for generating 2022 may optionally comprise means fordemodulating 2024 the received transmission signal, means for decoding2025 the demodulated transmission signal, and means for filtering 2026the demodulated and decoded transmission signal for removing thesubcarrier signals overlapping the modulated second carrier signal inbandwidth.

Then, e.g. the optional means for subtracting 2028 of the means forretrieving 2021 may perform subtracting the generated replica of thesecond carrier signal from the received transmission signal.

Finally, e.g. the optional means for transforming 2029 of the receiver202 may perform transforming the signal resulting from the subtractingfrom time domain into frequency domain.

Alternatively, as shown in FIG. 7, the means for retrieving of thereceiver 202 may also comprise means for decoding 2021 a the receivedtransmission signal, means for filtering 2021 b the decoded transmissionsignal for removing the subcarrier signals overlapping the modulatedsecond carrier signal in bandwidth, means for detecting 2021 c amidamble in at least one signal burst of the second carrier signal basedon a reference midamble, means for extracting 2021 d the midamble fromthe current signal burst, means for estimating 2021 e current channelinformation from the extracted midamble; and means for processing 2021 fsymbols sent via the first carrier signal based on the estimated currentchannel information during a subsequent burst of the second carriersignal after the at least one burst.

Finally, as shown in FIG. 9, another example of the present inventionmay also cover means for distributing, in unoccupied control channelelements of the first carrier signal having the first bandwidth, atleast a portion of the second carrier signal having the second bandwidthby using different control channel configurations in at least oneneighboring cell, the first bandwidth being greater than the secondbandwidth.

As for further refinements of the apparatuses according to an example ofthe present invention, the first carrier signal may be a long termevolution carrier signal, and the second carrier signal may be a globalsystem for mobile communications carrier signal. In addition, thetransforming from time domain into frequency domain may be a (fast)Fourier transformation, and the transforming from frequency domain intotime domain may be an inverse (fast) Fourier transformation. Stillfurther, the timing information may an orthogonal frequency divisionmultiplexing guard interval, and the channel information may channelstate information. Moreover, the queuing may be performed based on afirst in first out queue. Finally, there may be a single means fortransmitting or a plurality of means for transmitting in a coordinatedmanner.

Furthermore, at least one of, or more of means for accommodating 203,means for transmitting 2011; 2011′, means for subtracting 2019, meansfor filtering 2013; 2026; 2021 b, means for calculating 2015, means forcombining 2018, means for transforming 2014; 2016, means for inserting2017, means for retrieving 2021, means for receiving 2023, means forgenerating 2022, means for queuing 2027, means for modulating 2025;2012, means for demodulating 2024, means for decoding 2021 a, means fordetecting 2021 c, means for extracting 2021 d, means for estimating 2021e, means for processing 2021 f, means for distributing and/or thetransmitter 201′/transmitter 201/receiver 202, or the respectivefunctionalities carried out, may be implemented as a chipset or module.

The present invention also relates to a system which may comprise theabove-described transmitter 201 (or transmitter 201′ in conjunction withaccommodator 203), the receiver 202 and the above-mentioned distributor.

Without being restricted to the details following in this section, theembodiment of the present invention may be summarized as follows: Theinvention resides in

1. the idea of efficient Combined Transmission of two (or more) radioaccess technologies (RAT) in a single frequency block, i.e., anarrowband system and a wideband system, by

maintaining a single wideband (LTE) carrier (surrounding the narrowband(GSM) carrier(s) in frequency domain), and

Not introducing explicit (GSM-to-LTE frequency) guard bands.

Combined Transmission may be the transmission from

a. a single RF, power amplifier, and antenna chain, or

b. multiple RF, power amplifier, and antenna chains in a coordinatedmanner.

2. A Pre-coding Solution on the transmitter side for counter-acting theinterference caused by the narrowband system (GSM) into the widebandsystem (LTE).

3. In a delay reduction method for serial interference cancellation usedon the receiver side for counter-acting the interference caused by thenarrowband system (GSM) into the wideband system (LTE).

4. In distributing via network planning different LTE Release 8 controlchannel configurations over the network in such a way that a significantpart or even a complete GSM network can be embedded into e.g. a 20 MHzcarrier LTE Release 8 network.

Feasibility of Invention:

Using Combined Transmission of GSM and LTE, the performance of LTE bothof the data and the control channels may be affected. Receiverinterference cancellation and transmitter pre-coding intend to reducedrastically the performance degradation.

1. Combined Transmission of GSM and LTE:

The principle of Combined Transmission of a narrowband carrier and awideband carrier is illustrated in FIG. 3 using the example of CombinedTransmission of GSM and LTE Release 8.

2. Pre-coding Solution for Combined Transmission of GSM and LTE:

One option is to apply a pre-compensation according to FIG. 4, where theeffective interference from the GMSK signal to each subcarrier of theLTE signals may be pre-subtracted. For that purpose the GMSK signal istransformed from the time into the frequency domain by the same FFT(fast Fourier transformation) as may be used at the LTE receiver for theLTE signal. Those subcarriers located at the transmission of the GMSKsignal are filtered out before subtraction of the interfering signalsper each subcarrier of the LTE signal.

The SC filter in FIG. 4 has a functionality for calculating theresulting distortion from the GSM to the LTE signal, taking the OFDM GIas well as CSI information of the radio channels into account. In caseof a combined transmission from a single power amplifier and antennalocation, common channel estimation may be applied. In case of twodifferent locations for the GSM and LTE transmission, the CSI estimationof the GSM signal may be transferred to the LTE processing unit.

In FIG. 5, the LTE OFDM signal and the GMSK signal is drawn above eachother. It can be seen that the symbol length of GMSK signals and the LTEOFDM signal have different length and that the OFDM signal has a GI,while GMSK has none. Due to shorter symbol length of the GMSK signal,there may result interference as a composition of several GMSK symbols.This may be quite severe and spread over the full frequency band as thelength of the OFDM symbol is not a multiple of the GMSK symbol length.

In case that there is a frequency selective radio channel with differentmultipath components, the resulting GSM to LTE interference may bedifferent, as the GMSK signal has no GI and has a shorter symbol length.For this reason, in case of frequency selective radio channels, thetransmitter may be provided with full channel information for properpre-distortion as explained above.

In the discussion of closed loop cooperative MIMO (multiple inputmultiple output), an extended feedback of CSI is considered which may beused for pre-distortion as well.

It is also possible to use the GSM frequency resources for LTE in casethe GSM carrier is not allocated (gain per not transmitted TDMA frame inbest case e.g. 5 ms, in worst case e.g. 4 ms).

3. Delay Reduction in Interference Cancellation for Receiver Solution toCombined GSM and LTE

For the time domain approach in FIG. 6, the signal separation may bedone at the receiver side. For this purpose, it is exploited that aninterferer with a much larger Rx power than the desired signal may beeasily detected and decoded and afterwards subtracted from the weakersignal. The reason is that the small user signal may not degradedetection of the strong signal significantly. For this reason, thereceiver may have two branches. The upper one is for the demodulation ofthe GMSK signal as used for GSM. The demodulated and decoded signal isthan used to generate a replica of the originally transmitted GSM signalincluding a copy of the low-pass filter (LPF). This signal is thansubtracted from the receive signal in the lower LTE branch, therebysubtracting the GSM to LTE interference.

The FIFO (first in first out queue) in FIG. 6 may be included forcompensation of the processing delay in the GSM branch. Afterwards, anFFT can be performed on the interference free Rx signal.

The GSM carrier bandwidth may be quite low with e.g. only 200 KHz sothat it might be quite often frequency flat. Otherwise, the frequencyselectivity of the radio channel may have to be replicated in thereceiver as well before subtracting of the interfering GMSK signal,based on according channel estimation.

IF (interference) cancellation is proposed for two different systems.While GSM may have a frame length of 20 ms, for LTE Release 8, a veryshort sub frame length of 1 ms may reduce the latency on the radio airinterface.

Optionally, the GSM signal may be channel decoded. As the LTE decodingmay take place e.g. after cancellation of the GSM signal, the LTE signalmay be delayed by the total processing duration of the GSM processingchain.

It is proposed to use CSI estimation for the GSM signal from the framesbefore, which will render an estimate.

The received signal{right arrow over (Y)}={right arrow over (X)} _(LTE) ·{right arrow over(H)} _(LTE) +{right arrow over (X)} _(GSM) ·{right arrow over (H)}_(GSM)can be represented by a Toeplitz matrix {right arrow over (Y)} and iscomposed of a LTE signal part {right arrow over (X)}_(LTE) and aninterfering GSM data part multiplied by the corresponding channelimpulse responses for LTE signal part {right arrow over (h)}_(LTE) andinterferer {right arrow over (h)}_(GSM). The received symbols aretransformed by the IC algorithm, which can be expressed by amultiplication of the received data matrix {right arrow over (Y)} by thefilter weighting vector {right arrow over (a)}. This is resulting in{right arrow over (Z)}={right arrow over (Y)}·{right arrow over(a)}={right arrow over (X)} _(LTE) ·{right arrow over (H)} _(LTE)·{right arrow over (a)}+{right arrow over (X)} _(GSM) ·{right arrow over(H)} _(GSM) ·{right arrow over (a)}

The filter weighting vector {right arrow over (a)} must fulfill theproperties{right arrow over (H)} _(GSM) ·{right arrow over (a)}=0; {right arrowover (a)}≠0; {right arrow over (H)} _(LTE) ·{right arrow over (a)}≠0

The filter weighting vector is estimated based on the CSI received inthe last GSM burst periods, prior to the current LTE sub frame. SinceLTE sub frame duration of 1 ms is not a multiple of GSM burst durationof 577 μs, the update of the IC filter configuration may happenasynchronous to the LTE sub frame periods. Averaging might be applied toget a more reliable CSI of the multiple user signals of the last burstdurations.

In this way, the delay in the LTE processing chain may be limited to theprocessing duration of a FIR (finite impulse response) filter whichmight require a depth of approximately 4 GMSK symbol periodscorresponding to approximately 16 μs.

4. Distributing via network planning different LTE Release 8 controlchannel configurations over the network in such a way that a significantpart or even a complete GSM network can be embedded:

In an LTE Release 8 system with a very low number of users per cell, thePDCCH (physical downlink control channel) and the PHICH (physical hybridautomatic repeat request indicator channel) control channels are ratherscarcely populated, such that empty Resource Element Groups or PhysicalResource Blocks can be identified for embedding narrowband (GSM)carrier(s).

Using network planning to distribute different control channelconfigurations and optimizations over neighbor cells allows for creatingsufficient options for embedding a significant part or a complete e.g.GSM network in a Reuse 1 LTE Release 8 network.

The example illustrated in FIG. 9 shows actual narrowband (GSM)embedding regions for a single configuration as well as potentialnarrowband (GSM) embedding regions due to other configurations e.g. for10 MHz. The narrowband embedding region for a single 10 MHzconfiguration with medium number of scheduled users offers 2.6 MHzfrequency spectrum. A 20 MHz carrier with a similar load andappropriately optimized may offer about a twice as large narrowbandembedding region per configuration. By varying control channelconfiguration and optimization, the union set of narrowband embeddingregions will offer sufficient spectrum for embedding a typical2×2×2-Sites GSM network.

Further Examples

For the purpose of the present invention as described herein above, itshould be noted that

an access technology may be any technology by means of which a userequipment can access an access network (or base station, respectively).Any present or future technology, such as WiMAX (WorldwideInteroperability for Microwave Access) or WLAN (Wireless Local AccessNetwork), BlueTooth, Infrared, and the like may be used; although theabove technologies are mostly wireless access technologies, e.g. indifferent radio spectra, access technology in the sense of the presentinvention may also imply wirebound technologies, e.g. IP based accesstechnologies like cable networks or fixed line.

a network may be any device, unit or means by which a station entity orother user equipment may connect to and/or utilize services offered bythe access network; such services include, among others, data and/or(audio-) visual communication, data download etc.;

generally, the present invention may be applicable in those network/userequipment environments relying on a data packet based transmissionscheme according to which data are transmitted in data packets and whichare, for example, based on the Internet Protocol IP. The presentinvention is, however, not limited thereto, and any other present orfuture IP or mobile IP (MIP) version, or, more generally, a protocolfollowing similar principles as (M)IPv4/6, is also applicable;

a user equipment may be any device, unit or means by which a system usermay experience services from an access network;

method steps likely to be implemented as software code portions andbeing run using a processor at a network element or terminal (asexamples of devices, apparatuses and/or modules thereof, or as examplesof entities including apparatuses and/or modules therefore), aresoftware code independent and can be specified using any known or futuredeveloped programming language as long as the functionality defined bythe method steps is preserved;

generally, any method step is suitable to be implemented as software orby hardware without changing the idea of the invention in terms of thefunctionality implemented;

method steps and/or devices, units or means likely to be implemented ashardware components at the transmitter and/or receiver, or any module(s)thereof, are hardware independent and can be implemented using any knownor future developed hardware technology or any hybrids of these, such asMOS (Metal Oxide Semiconductor), CMOS (Complementary MOS), BiMOS(Bipolar MOS), BiCMOS (Bipolar CMOS), ECL (Emitter Coupled Logic), TTL(Transistor-Transistor Logic), etc., using for example ASIC (ApplicationSpecific IC (Integrated Circuit)) components, FPGA (Field-programmableGate Arrays) components, CPLD (Complex Programmable Logic Device)components or DSP (Digital Signal Processor) components; in addition,any method steps and/or devices, units or means likely to be implementedas software components may alternatively be based on any securityarchitecture capable e.g. of authentication, authorization, keyingand/or traffic protection;

devices, units or means (e.g. transmitter and/or receiver, or any one oftheir respective means) can be implemented as individual devices, unitsor means, but this does not exclude that they are implemented in adistributed fashion throughout the system, as long as the functionalityof the device, unit or means is preserved;

an apparatus may be represented by a semiconductor chip, a chipset, or a(hardware) module comprising such chip or chipset; this, however, doesnot exclude the possibility that a functionality of an apparatus ormodule, instead of being hardware implemented, be implemented assoftware in a (software) module such as a computer program or a computerprogram product comprising executable software code portions forexecution/being run on a processor;

a device may be regarded as an apparatus or as an assembly of more thanone apparatus, whether functionally in cooperation with each other orfunctionally independently of each other but in a same device housing,for example.

Although the present invention has been described herein before withreference to particular embodiments thereof, the present invention isnot limited thereto and various modification can be made thereto.

For ease of clarity, the following table provides a survey of theabbreviations used in the above description. It is to be noted that an“s” following an abbreviation represents the plural of thatabbreviation, e.g. “GIs” represents “guard intervals”.

3GPP: 3^(rd) generation partner ship project LTE: Long term evolutionA&F: amplify and forward BS: base station CDD: cyclic delay diversityCSI: channel state information D&F: decode and forward DL: downlink FDD:frequency division duplexing GI: guard interval HARQ: hybrid automaticrepeat request LOS: line of sight MS: mobile station MCS: modulation andcoding scheme MIMO: multiple input multiple output NB: Node B OFDM:orthogonal frequency division multiplexing OFDMA: orthogonal frequencydivision multiple access R8: Release 8 RN: relay node RS: referencesignal RB: resource block SC: subcarrier TDM: time domain multiplexingUE: User equipment UL: uplink

The invention claimed is:
 1. A method, comprising: retrieving a firstcarrier signal from a received transmission signal comprising aplurality of subcarrier signals of the first carrier signal, each ofwhich subcarrier signals being interfered by an effective interferenceof a modulated second carrier signal wherein the retrieving is performedby subtracting a generated replica of the second carrier signal from thereceived transmission signal; prior to the subtracting, generating thereplica of the second carrier signal by: demodulating the decodedtransmission signal; decoding the received transmission signal; andfiltering the demodulated and decoded transmission signal for removingthe subcarrier signals overlapping the modulated second carrier signalin bandwidth.
 2. The method according to claim 1, further comprising,prior to the retrieving, receiving the transmission signal.
 3. Themethod according to claim 1, wherein the retrieving further comprises,after the subtracting, transforming a signal resulting from thesubtracting from a time domain into a frequency domain.
 4. The methodaccording to claim 2, further comprising, after the receiving and priorto the retrieving, queuing the received transmission signal.
 5. Themethod according to claim 1, wherein the retrieving is performed by:decoding the received transmission signal; filtering the decodedtransmission signal for removing the subcarrier signals overlapping themodulated second carrier signal in bandwidth; detecting a midamble in atleast one signal burst of the second carrier signal based on a referencemidamble; extracting the midamble from the current signal burst;estimating current channel information from the extracted midamble; andprocessing symbols sent via the first carrier signal based on theestimated current channel information during a subsequent burst of thesecond carrier signal after the at least one burst.
 6. The methodaccording to claim 3, wherein at least one of the following applies: thefirst carrier signal is a long term evolution carrier signal; the secondcarrier signal is a global system for mobile communications carriersignal; the transforming from time domain into frequency domain is oneof a Fourier transformation and a fast Fourier transformation; thetransforming from frequency domain into time domain is one of an inverseFourier transformation and an inverse fast Fourier transformation; thetiming information is an orthogonal frequency division multiplexingguard interval; the channel information is channel state information;and the queuing is performed based on a first in first out queue.
 7. Theapparatus according to claim 1, further comprising means for receivingthe transmission signal prior to the retrieving performed by the meansfor retrieving.
 8. The method according to claim 1 performed with anon-transitory computer readable medium storing a computer programproduct, the computer program product executed by a processor.
 9. Themethod according to claim 1, wherein the first carrier signal and thesecond carrier signal are communicated using different accesstechnologies.
 10. The method according to claim 1, wherein the firstcarrier signal and the second carrier signal are transmitted from asingle antenna or from multiple different antenna, respectively, fortransmitting.
 11. The method according to claim 1, wherein the firstcarrier signal and the second carrier signal are transmitted in a firstbandwidth and a second bandwidth, respectively, and the first bandwidthadjoins to or overlaps the second bandwidth.
 12. An apparatus,comprising: means for retrieving a first carrier signal from a receivedtransmission signal comprising a plurality of subcarrier signals of thefirst carrier signal each of which subcarrier signals being interferedby an effective interference of a modulated second carrier signal,wherein the means for retrieving further comprises means for subtractinga generated replica of the second carrier signal from the receivedtransmission signal; means for generating, prior to the subtractingperformed by the means for subtracting, the replica of the secondcarrier signal, the means for generating comprising: means fordemodulating the decoded transmission signal; means for decoding thereceived transmission signal; and means for filtering the demodulatedand decoded transmission signal for removing the subcarrier signalsoverlapping the modulated second carrier signal in bandwidth.
 13. Anapparatus comprising: at least one processor; and at least one memoryincluding computer program code, where the at least one memory and thecomputer program code are configured, with the at least one processor,to cause the apparatus to at least: retrieve a first carrier signal froma received transmission signal comprising a plurality of subcarriersignals of the first carrier signal, each of which subcarrier signalsbeing interfered by an effective interference of a modulated secondcarrier signal wherein the retrieving is performed by subtracting agenerated replica of the second carrier signal from the receivedtransmission signal; prior to the subtracting, generate the replica ofthe second carrier signal by: demodulating the decoded transmissionsignal; decoding the received transmission signal; and filtering thedemodulated and decoded transmission signal for removing the subcarriersignals overlapping the modulated second carrier signal in bandwidth.14. The apparatus according to claim 13, wherein the first carriersignal and the second carrier signal are communicated using differentaccess technologies.
 15. The apparatus according to claim 13, whereinthe first carrier signal and the second carrier signal are transmittedfrom a single antenna or from multiple different antenna, respectively,for transmitting.
 16. The apparatus according to claim 13, wherein thefirst carrier signal and the second carrier signal are transmitted in afirst bandwidth and a second bandwidth, respectively, and the firstbandwidth adjoins to or overlaps the second bandwidth.
 17. The apparatusaccording to claim 13 embodied in a base station or a user equipment.18. The apparatus according to claim 13, wherein the at least one memoryincluding the computer program code is configured with the at least oneprocessor to cause the apparatus to, after the subtracting, transform asignal resulting from the subtracting from a time domain into afrequency domain.